Valves have been proposed for regulating fluid flow which utilize over-travel of a valve handle past that required to open or close the fluid passage so as to exert a compressive pressure on an expansible elastomeric plug in a manner expanding it outwardly against the surrounding walls for forming a seal. One of these valves is shown in U.S. Pat. No. 3,260,498. Although such valves are advantageous in eliminating gaskets, packings, and the like, they have drawbacks among which is the fact that such compressed expanded plugs extrude into the openings for the flow passage and thereby make it very difficult to open the valve and indeed in many instances destroy the plug by disrupting the material thereof as the parts of the plug that are extruded into the flow passage openings resist motion past the edges of the same and become sheared or fractured.
I am also familiar with U.S. Pat. No. 2,552,991, McWhorter, dated May 15, 1951, cited in my Pat. No. 3,907,251. This patent will be further discussed in connection with the preferred form of my invention which will be more fully described hereinafter.